The present invention is related to a method for increasing structural strength of spokes, and more particularly to a processing method which can increase the shear strength of the neck section and bending section of the spoke and increase the cross-sectional area thereof.
Taiwanese Patent Publication Nos. 261953, 317821, 385284, 398423, 4485851, 516517 and 511588 disclose structures for connecting the hub with the spokes of a wheel of a bicycle or a motorcycle. The above Patents provide measures for more conveniently assembling and disassembling the spokes. However, it is not considered that the spokes may be broken due to insufficient structural strength.
The spokes are mostly made of metal wire material such as carbon steel, stainless steel, titanium, alloy, etc. The selected wire material has good resilience and tensile strength. However, the shear strength of the metal is only about half the tensile strength. This is the major reason why the spoke always breaks first at the neck section. In a tension test of the spoke, the same result is obtained, that is, the neck section of the spoke is shorn (as shown in FIG. 1, wherein point B bears greatest shearing force).
To a wheel, in case one single spoke is broken, the other spokes will suffer uneven force and successively break. This will lead to danger to a rider.
Many trials have been made by manufacturers to reform the spoke structures (as Table 1). Mainly, the diameter of the wire is enlarged (or partially enlarged). This is effective. However, the consumption of material is increased and the weight of the product is increased. Therefore, this measure is not widely used. With respect to the spoke with partially enlarged diameter (such as double butted spoke and swaged spoke), the larger diameter wire is ground or swaged to partially reduce the diameter. The processing cost is high and the product still has considerable weight. In other words, it seems that it is impossible to satisfy all the requirements for low cost, light weight and high strength.